The present invention relates to the testing of prosthetic heart valves, or similar valves.
Representative of the prior art is Swanson U.S. Pat. No. 4,381,663, in which are set forth apparatus and methods by which test samples such as heart valves are tested in a closed fluid environment by oscillating flow of a bellows-actuated fluid oscillator.
A particular need arises in the durability-fatigue testing of biological tissue prosthetic heart valves. To be tested properly such heart valves may be conducted in a sterile human blood plasma environment at normal body termperature, 37.degree. C.
In the testing of such heart valves, it may be desired to carry out a testing of several at the same time. The valves may vary from valve to valve, and it is desirable to be able to test each under the same operating conditions so as to achieve a desired degree of control for comparative purposes.
Accordingly, it is an object of the present invention to provide an improved apparatus for testing of heart valves by the provision of a system making closed durability, or fatigue tests on a number of different samples at the same time.
Specifically, an object of the present invention is the provision of such apparatus and methods for testing of prosthetic heart valves in a sterile blood plasma, or other fluid environment at body temperature.
It is another object of the invention to provide such testing apparatus and methods for carrying out the testing of heart valves in a preselected fluid medium at a desired temperature.
It is also an object of the present invention to provide such apparatus wherein testing may be carried out automatically and without supervision with assurance that testing of the apparatus will automatically terminate in the event of a failure, undesired condition, excessive temperature or the like.
Yet another object of the invention is the provision of such testing apparatus and methods which provide repetitive stressing of the heart valve at a high frequency which may be considerably greater than that at which the sample under test would normally be flexed in use, thereby greatly accelerating the life testing of such sample.
Another object of the invention is the provision of such testing apparatus and methods wherein a number of different valves being tested at one time may be varied from test to test, and wherein the number of samples under test does not influence the test conditions in a deleterious or disadvantageous way.
The invention has as another object the provision of such testing apparatus and methods which are extremely compact and which minimize the volume of test fluid being utilized, as well as minimizing the cubage of the apparatus, and providing apparatus which operates with extreme efficiency and little input power.
Yet another object of the invention is the provision of such test apparatus and methods which allow substantial variation in the amplitude of the stresses applied to the sample during test, and permitting the amplitude to be very readily and easily changed without disturbance of other aspects ot the test, while providing nevertheless testing apparatus and methods which permit a wide range of testing conditions, including different termperatures, pressures, frequencies and stresses.
Among still other objects of the invention include the provision of such testing apparatus which: provides testing in a completely sealed fluid environment; economizes in the use of test fluids; provides extremely high test visablility and ease of insertion and removal of test samples and high accessibility thereof; permits test fluid to be easily filled, emptied and/or removed, and facilitates cleaning of the apparatus.
Briefly, valve testing apparatus for testing of test samples, i.e., valves, in accordance of the invention by application of repeated oscillatory forces produced by fluid motion relative to the sample includes a chamber for receiving a plurality of test samples, the chamber being such as to define individual fluid flow passages communicating with respective test samples for directing an oscillating flow of fluid of such test samples. Plural bellows are connected with each of the respective fluid flow passages, with which they are arranged in a circular pattern, and a swash plate is positioned below the bellows, with means for rotatably driving the swash plate oscillatorily to provide corresponding alternate expansion and contraction of the bellows. A further fluid passage is connected with the test samples for providing a fluid path extending from one of the bellows, into the test sample, through the further fluid passage, through another test sample, and to another bellows, by the opposite side of the swash plate. The swash plate, with adjustable tilt axis, causes alternate contraction and expansion of the bellows on opposite sides of the swash plate to alternately expose the test samples to oscillatory fluid forces.
A bypass passage carries the flow while a valve is closed. The inertial reaction of the fluid in this passage during flow acceleration determines the pressure loading on the valve.
An electric heating device and a temperature probe are utilized for controlling the temperature of the fluid in the apparatus, such as to provide, for example, tests under conditions typical of the human blood plasma environment at 37.degree. C.
Other objects and features will be in part apparent and in part pointed out hereinbelow.